A comparative investigation of syngas and biofuel power and hydrogen plant combining nanomaterial-supported solid oxide fuel cell with vanadium-chlorine thermochemical cycle

Abstract

In order to realize combined advantage of hydrogen and renewable energy systems, two new cogeneration of hydrogen and electricity frameworks are developed, examined and compared. The SOFC unit is applied for power production, while its waste heat is suggested to be converted to hydrogen by a thermochemical vanadium-chlorine cycle. As this method requires no electricity input, it is highly preferred to common electrolysis-based techniques for hydrogen production. The systems are fueled by algae biomass converted by either digestion or gasification for provision of biogas or syngas fuels. A theoretical investigation is presented to appraise the systems’ practical feasibility according to the violations imposed by thermodynamics’ laws. In addition to detailed thermodynamic analyses, exergo-environmental studies are reported to estimate negative impacts of the considered frameworks. Through a sensitivity study, the influence on performance (efficiencies and product generation amounts) of design conditions are comprehensively described. The findings have shown that, generally the biogas-powered framework outperforms the syngas-powered one and the amount of superiority depends on operating conditions, ranging from 3 to 10%. Also, it is found that the syngas-powered system can generate more hydrogen and thus, if the hydrogen production is more significant than power generation the biomass gasification would be preferred over the digestion. The exergy destruction assessment within components of the two systems has indicated larger values for gasifier compared to digester due to higher rate of chemical reactions and larger temperature differences.